The long-range goal of the project is to investigate the structure, function and biosynthesis of the glycoprotein alpha-1-antitrypsin which is the major protease inhibitor of plasma. Whereas the most common variant (PiM) is present at 1.3 mg per ml, the marked deficiency in alpha-1-antitrypsin that occurs in subjects with the PiZZ phenotype is predisposing to pulmonary emphysema and juvenile hepatic cirrhosis. A major aim is to characterize the structure of the oligosaccharide side chains of the M- and Z-type glycoproteins by exoglycosidase analysis, Smith degradation and methylation analysis in order to define the precise defect in the oligosaccharide chain(s) of the Z-protein. Similar structural studies will also be performed on glycopeptides derived from cyanogen bromide digests of rat serum alpha-1-antitrypsin. Detailed knowledge of the structure of the rat glycoprotein will facilitate our studies on the biosynthesis of alpha-1-antitrypsin and the regulation of protease inhibitor levels in plasma. We will also investigate the control mechanism responsible for permitting the maintenane of alpha-1-antitrypsin levels in protein-calorie malnutrition using the rat as a model. A major aim of the project will be to investigate the influence of the peptide region of a glycoprotein on specificity of the sialyltransferase that catalyzes the addition of terminal N-acetylneuraminic acid residues to its oligosaccharide chains. Sialyltransferase purified from human liver will be used to explore the sialic acid acceptor properties of various asialo-glycopeptides prepared from human alpha-1-antitrypsin. These studies will provide a better understanding of the chemical structure and biosynthetic steps involved in the transport and secretion of alpha-1-antitrypsin and the regulation of plasma glycoprotein concentrations.